What happens when a second mars appears?

Sp33df0rc3

Hi,

As you can see, i'm new to this forum, but i saw some of the other questions being posted and hoped someone might be able to answer my question:

essentially, if a second mars were to be constructed (lets say in a few hundred years) so that it has the same density as Mars I and is in the same orbit, but directly opposite Mars I.

1. How catastrophic would this be for the solar system?
2. would moving one of Mars I's moons to Mars II be further catastrophic?
3. If it's not catastrophic, how much would it distort the layout of the solar system?

I realize that some of what I'm asking is quite large, but I'm not an incredibly physics minded person.

If anyone is particularly interested, I was hoping to try and map out what the system would look like with this additional planet, so if anyone is interested in helping out...

:D

thanks, and apologies if this seems like a silly question.

zhermes

Such an addition would have very minor effects on the rest of the solar system. The effect of the moons would be entirely negligible.

The main result would be destabilization of the mars (I and II) systems, in which one could be ejected, or they could collide, etc.

From a newtonian standpoint, the system would be stable, but higher-order effects might destroy that stability. One would have to perform a perturbation analysis to find out....

Nik_2213

Sadly, the point *opposite* a planet is not stable. You need to put it in L4 or L5, those +/-60 degree positions. Even then, there will be tidal effects from eg Jupiter that would destabilise it in long term.

IIRC, the Mars-sized BigSplatter whose collision with proto-Earth formed our Moon is now thought to have formed at Earth's L4 or L5 position, otherwise the closing speed would have been excessive. FWIW, mega-impactors are thought to have caused Mars' lopsided (N/S) crust and stripped most of Mercury's...

qraal

There would be no catastrophic effects for the other planets in the short term, but in time the chaotic interactions between the two "twin planets" would result in them either colliding or careening around the Solar System across the orbits of the other planets. That would be catastrophic... or maybe not. A complicated orbit between the two which causes them to oscillate in their mutual orbit might be possible, though it would require the occasional bit of planet maneuvering to keep it stable against perturbations by Jupiter and Saturn.

If they can be kept in place, then the long term effect on the Inner Planets might be to increase their mutual chaotic perturbations. Mercury, even without the extra planet, is already in a potentially unstable orbit, which will chaotically amplify its eccentricity over a few aeons and cause it to crash into Venus or Earth or even be ejected from the Solar System. Of course, if we can make/move planets, then parking Mercury in a long term stable orbit around Venus might be the better option.

As the Sun brightens inexorably towards the end of its Main Sequence, then chaotic planet effects will be needed to shift the Inner Planets outwards from the Sun, to prevent their ultimate immolation in the Sun as it expands in 7.5 billion years. An option might be to park the Inner Planets around Jupiter as new moons, then use its hydrogen/helium in a gigantic fusion rocket to shift further away from the Sun. Larry Niven did something like that fictionally in his novel "World Out of Time".

DaveC426913

Mars is pretty small. It would have little effect on other planets, even when crossing their orbits - unless by a very slim chance, they were in the same neighborhood.